1. Field of the Invention
The present invention relates to a radial seal of a rotary piston engine with a trochoidal-shaped housing runway or casing internal surfacing and multi-corner piston, with which sealing strips are arranged in radial grooves in the corners of the piston; these sealing strips, under pressure of the working or operating chambers of the rotary piston engine, engage against the raceway or casing inner surfacing and respectively also engage against the suction side groove wall.
2. Description of the Prior Art
Such sealing strips, especially as located in a piston corner and as considered in piston rotational direction as to the expansion chamber before passage thereof through a dead-center position, are subject to a special stress or strain; in other words, the trailing radial seals of the expansion chamber before passing the dead center position are subject to stress and wear which leads to wear phenomenon or appearance as to the sealing strip crest, arch, dome or apex on the preceding side thereof as well as leading to corresponding wear or material removal along the housing raceway or casing inner surface.
These disadvantages are not so critical with the sealing strip preceding the expansion chamber as a consequence of the small or nominal inclination thereof with respect to the mantel or housing raceway or casing internal surfacing, although otherwise however being equal. The wear phenomenon or appearances could be reduced or avoided by corresponding material matching, when no concern or care has to be taken as to higher cost expenditure, for example for ceramic strips. Thereby however there cannot be prevented an increase of the friction via a striking engagement that is too strong and pressing of the sealing strips against the mantel or housing raceway or casing inner surfacing. Actually, in itself, the friction resistance with rotary piston engines, especially with motors, is smaller or more nominal than with stroke lifting-cylinder machines. This advantageous relationship at higher rotary speeds and load conditions reverses because of the sealing strips engaged or impinged with a pressure that is too high.
The foregoing mentioned problems result moreover primarily with combustion motors, since here the working or operating pressure rises very quickly and namely still in the time in which the sealing strip of the expansion chamber stands or is located in an acute angle to the raceway, runway or inner operating surfacing of the casing of the rotary piston engine. The friction losses take effect and assume significant however respectively according to rise of the working or operating pressures also with compressors.
The force of the pressure gases for pressing into engagement in the groove space is dependent upon the size of the surfaces of the sealing strip toward the groove base. In German Offenlegungsschrift No. 24 27 062 Maddock dated Jan. 2, 1975 there is described a sealing strip that is made more narrow as far as to half the normal width thereof; in other words, the sealing strip is decreased to only one half of the normal thickness in circumferential direction and in order to form a reduced admission surface on its underside lying opposite to the groove base as to the pressure gases. This strip however is constructed L-shaped on the side thereof toward the mantel runway or casing inner surface. The arm of the L shaped strip extending in circumferential direction is located upon the pressure side for a purpose, also effecting or bringing about, that the pressure gases can engage more quickly therebelow or underneath such arm of the sealing strip. The impingement or engagement surface that effects or brings about the pressing of the sealing strip against the mantel raceway or casing inner surfacing accordingly is considerably enlarged, or practically doubled dimensionally. In addition, the sealing strip is unsymmetrical and consequently considered only as a following or only as a preceding seal respectively according to the positioning of the arm of the L relative to the rotational direction in fulfilling the purpose of such sealing strip.